Techniques of setting off the defects of different kinds of films by laminating them into a composite have been known heretofore in the field of packaging bags. Particularly, in the field of packaging foodstuffs, laminated packaging bags composed of a resin layer having excellent transparency, mechanical properties, rigidity, heat resistance and gas-barrier property, such as polypropylene, a polyester, nylon, cellophane or an ethylene/vinyl alcohol copolymer, and a resin layer having good transparency and heat sealability, such as polyethylene, polypropylene or an ethylene/vinyl acetate copolymer have come into widespread use.
In order to produce such laminated packaging bags, there is usually employed a method which comprising heat-sealing the top and bottom end portions or all end portions of a film, and in the resulting bag, the innermost layer is a resin layer having good heat sealability. Accordingly, films use as the innermost layer of the packaging bags are required not only to have good heat sealing characteristics but also to be free from extraction or degradation of the resin components which may be caused by an article packaged therein. In recent years, there have been a variety of articles to be packed and a variety of modes of using the packaging materials and some problems have arisen with regard to films which have heretofore been used to form the heat sealed layer. These problems include, for example, the high and narrow heat-sealing temperature range of polypropylene films, the poor heat resistance, strength and oil resistance and acetic acid odor of ethylene/vinyl acetate copolymer films, the poor heat sealing strength and hot tack property of films of high-pressure low-density polyethylene, and the poor flexural resistance of each of such films which is likely to lead to the formation of pinholes in bags during handling in transportation, etc. and to cause leakage of the contents.
The present invention has successfully given a solution to the above new problems, and as will be described below in detail, provides an ethylene/alpha-olefin copolymer composition having excellent low-temperature heat sealability, heat seal strength, flexural resistance, transparency and impact strength and being suitable for packaging films.